Since prostaglandins (PG) have marked effect on renal vascular and tubular functions several physiological roles have been suggested for them. The objective of the proposed project is to investigate the renal actions of infused (exogenous) PG and compare it with the effects of released (endogeneous, renal PG using recollection micropuncture and tubular microinjection techniques in rats. Indomethacin, a potent inhibitor of PG synthesis, will be used to dissect and identify changes in renal function that are produced by PG. The mechanism of action of PG on the renal handling of sodium and water will be examined parallel with their vasodilator action, permitting an evaluation of the correlation between their tubular and vascular effects. With the use of micropuncture techniques the nephron segment, in which PG exert their inhibitory action on tubular reabsorption can be identified directly. Whether they act primarily from the peritubular or luminal side, will be examined by injecting PG directly into the tubular lumen at different sites. The mechanism of action of PG on renal water excretion will be evaluated, in addition to the micropuncture experiments by relating PG action to cAMP concentration in renal tissues and renal venous outflow. If prostaglandins increase water excretion primarily by opposing adenylate cyclase activation by ADH, then an inverse correlation should exist between cAMP concentration and prostaglandin activity. The results of the proposed work will facilitate our understanding of how the tubular effects of these fatty acids relate to their role in the integration of renal vascular and tubular functions in the kidney's overall contribution to BP regulation.